Electrode for diathermy apparatus or the like



April 17, 1951 G. TAWNEY I 7 2,549,399

ELECTRODE FOR DIATHERMY APPARATUS OR THE LIKE Filed 00 12. 10, 1947 2 Sheets-Sheet 1 FIG.

2 in! 28a SHQRTWAVE %i 3 GENERATOR INVENTOR GERELD L. TAWNEY WM EM I ATTO RN EY April 17, 1951 G. TAWNEY 2,549,399 ELECTRODE FOR DIATHERMY APPARATUS OR THE LIKE Filed Oct. 10, 1947 2 Sheets-Sheet 2 FIG. 5. FIG. 6.

. v INVENTOR GERELD L. TAWNEY ATTORNEY in the subject.

Patented Apr. 17, 1951 ELECTRODE FOR DIATHERMY APPARATUS OR THE LIKE Gercld L. Tawney, Hempstead, N. Y., assignor of sixty per cent to Atlantic Electronics .Oorporas tion, Port Was i t a c rp ra on of New York, and forty per cent to Morris Reison,

Great Neck, N. Y.

Application October 10, 1947, Serial No. 779,119

(Cl. 128 4l13) 12 Claims.

The present invention relates to the art including short-Wave diathermy apparatus, and is more particularly concerned with improvements in electrodes for such apparatus useful in applying the short-wave energy produced by the apparatus to a subject to be treated.

At the present state of the art, it is Well-known to use high-frequency or shortewave oscillations for physiotherapy purposes, to produce internal and/or surface heating within the body for therapeutic benefit. Diathermy apparatus for these purposes essentially comprises a simple short- Wave oscillation generator in combination with special means for usefully applying .the generated h rt-W Power to the subject to be treated. Because of'the Wide variations in the character of the electrical loading upon the apparatus during normal use, .difficulty has been experienced in providing apparatus adaptable for satisfactory performance during all normally encountered operating conditions. In particular, difliculty is encountered in maintainin s bst nti lly c nstant frequency, Within the vrequirements imposed by the Federal Communications Commission. Further difliculty flows from the previous necessity of providing a very high voltage at the output terminals of the machine, in order to get suflicient power to the subject; such high voltage frequently results in sparking-over between condenser plates within the apparatus, or may even puncture the cables connected to these terminals. Still further trouble is encountered in providing ready adjustability for the output, without undue sensitivity of control, and also in preventing external influences, such as nearby objects, from harmfully affecting the performance of the apparatus.

A favorite method in the prior art for connecting the diathermy machine to supply energy to the subject has been to connect a pair of electrodes to the respective output terminals of the machine by means of respective cables and to placethe subject between these electrodes, whereupon the oscillating high-frequency held between the electrodes produces the desired heating with- A customary form which such electrodes have taken is as flat metallic plates covered by insulation. In one application, these electrodes are known as pads and are applied directly to the subject, so that only the insulation The ,operator is also subject to the hazard of c covering separates the metal plate from the subject. It was early discovered that a preferred form of treatment was obtainable by separating the pad electrodes from the subject by a suitable air space. .Such electrodes are known as air- III spaced electrodes. With the use of such air.- spaced electrodes, the above-mentioned difficultie of spark-over and cable puncture frequently occur. Also, the adjustment of power how to the subject is rendered noneuniforrn and relatively sensitiyerthat is, relatively small adjustment of the control causes a large change in effect upon the subject. Furthermore, a very high voltage is required between the electrodes, resulting in the possibility of arceover to nearby grounded metal? objects, even through insulation, which may thereby be injured. Also, this high voltage rene ders the apparatus sensitive to the approach .of nearby objects, even the ,operator, and to move ment of the subject, so that the heating effect upon the subject is not consistent and may vary as the operator moves around in the vicinity.

spark burns if he gets too close to the electrodes or their supports. These effects seem to be inherent in the conventional type .of air-spaced electrode, apparently due to the .very small series capacitance introduced into the system by the spacing between electrode and subject.

A further type of electrode Which has been proposed in Rose Patent No. 2,130,758 is a fiat spiral with one or both ends open, and the lead connected at an end or in the center. An important problem encountered in the use of such an electrode is that of spark-over from the unconnectedend of the spiral, lack of uniform heating of the subject over the surface of the subject 7 between the electrodes, and the attainment-of evenness and lack of sensitivity of control action.

According to the present invention, these former objections and disadvantages of the airspaced electrode are substantially minimized and almost removed entirely by the use of a novel form of electrode readily adapted to air-spaced use, and permitting Wider air-spacing than prior know-n electrodes. This electrode substantially reduces the voltage required for satisfactory heating eliect, and thereby minimizes the difiiculties due to spark-over and nearby objects. Also, this electrode permits a fairly even control of power flow to the subject over the entire range of adjustment, without undue sensitivity.

In a preferred form, the electrode of the present invention comprises a flat spiral conductor, similar to the Rose spiral electrode described above, with the additional-improvement that one end (preferably the outer end) of the spiral is connected to a closed or short-circuited conductive loop, the other end of the spiral being con nected to the lead from the machine. The simple expedient of the addition of the closed loop to the spiral has the effect of overcoming the disadvantages inherent in the plain spiral electrode, and provides an electrode which meets the longsought requirements of this field. Many modifications of this electrode, all coming within the broad principle of using a closed loop, are possible while retaining substantially the advantages of my preferred embodiment.

Accordingly, it is a primary object of the present invention to provide an electrode for diathermy apparatus or the like, which minimizes spark-over diihculties, permits a relatively low voltage at the diathermy machine and at the electrodes without interfering with sufficient power flow to the treatment subject, provides a smooth, even, non-sensitive control of heating of the subject and also provides nearly uniform heating over the area of the subject being treated.

It is a further object of the present invention to provide an improved and novel diathermy electrode having a conductive coil, which may be in the form of a flat spiral, in combination with a closed or short-circuited conductive loop.

It is another object of the present invention to provide an improved and novel diathermy electrode using a closed loop connected to a coil.

It is still another object of the invention to provide improved electrodes for diathermy apparatus of the like, of the single or two-conductor lead-in types, using a short-circuited conductive loop.

Other objects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the appended drawings, in which Fig. 1 is a schematic diagram of a diathermy machine and its electrodes and their coupling thereto;

- Fig. 2 is a perspective view of the electrode of the present invention in an adjustable support providing adjustable air-spacing, as desired;

Fig. 3 is an enlarged exploded perspective view of a preferred form of the present electrode, showing its casing;

. Fig. 4 is a plan view of an improvement on the electrode of Fig. 3;

Fig. 5 is a plan view of a slightly modified version of the electrode of Fig. 4;

Figs. 6-10 are plan schematic views of modified electrodes embodying the basic principles of the present invention.

Referring to the drawings, Fig. 1 shows schematically the general system of a diathermy machine and its connection to a subject to be treated. This system includes a short-wave generator 2| of any suitable type, many forms of such generator for diathermy purposes being known in the art. One suitable form is shown in Tawney-Cakes application S. N. 728,318, filed February 13, 1947, now abandoned. Generator 2| is coupled to (or has as part of it) a tank circuit 22 which primarily determines the operating frequency of the apparatus.

The tank circuit 22 is loosely coupled to an output coil 23 which may have very few turns, such as one to three. One end of output coil 23 is connected directly to one output terminal 24 of the diathermy machine, while the other end of coil 23 is connected to the other output terminal 24a in series with a control or tuning condenser 26. As will be seen, adjustment of condenser 28 controls the output power delivered to the subject being treated.

, The subject being treated is indicated schematically at 21, and a pair of electrodes 28, 280. are spaced on either side thereof. The electrodes 28, 28a are connected to the terminals 24, 24a by respective cables 29, 29a.

In actual use, the electrodes 28, 28a are usually spaced slightly (such as of the order of 1 inch or less) from the subject 21, which has been found to reduce the danger of surface burns, and to improve the operation somewhat. It will be seen that the air-spacing introduces an effective series capacitance between each electrode 28, 28a and the subject 21, which itself usually has a lossy capacitance impedance. The net result of the air-spacing is to materially increase the impedance coupled between electrodes 28, 28a so that, for a given high-frequency current flowing to the subject, a much higher voltage between electrodes is required. This increases the danger of spark-over from each electrode to any nearby grounded object, which may frequently impair the insulation in which the electrode is mounted.

This situation also necessitates a high voltage between the terminals 24, 24a of the apparatus, so that not only the electrodes, but also the cables and the terminals are subject to high voltage. This high terminal and cable voltage renders the cables liable to puncture where they may happen to touch one another or to touch any grounded part of the apparatus, such as the casing or electrode support.

In addition, difficulty is experienced with respect to condenser 26. As already stated, the amount of power flow is controlled by condenser 26, which may be considered to vary the impedance coupled across output coil 23, and thereby to vary the power delivered to the cables 29, 29a and to the subject 21. In manipulating condenser 26, due to the phase of the high-frequency current, a very high reactive voltage can be created across condenser 26, which may be even higher than the voltage across terminals 24, 24a. As a result, spark-over between condenser plates often occurs, which may completely damage the condenser so as to require replacement.

Also, the air-spacing of electrodes causes the load impedance and terminals impedance to be so large relative to the impedance of condenser 26 that even a slight adjustment of the condenser 26 causes a very material variation in heating of the subject. This sensitivity varies in different portions of the adjustment range, and for different types of subject, and creates a series disadvantage in using the apparatus.

The above discussion of the prior art practice is necessary to appreciate the operation and advantages of the present invention, shown in the succeeding figures. Figure 2 shows an electrode mounting providing adjustable air-spacing, which the present invention makes feasible. The electrode assembly 3| is formed as a disk mounted coaxially upon a rod 32 which is adjustably supported in a ring 33 having a set-screw 34 for fixing rod 32. Rod 32 is hollow, and carries the end of cable 23 or 290. which is thus connected to the electrode itself. Ring 33 is fixed rigidly on the end of arm 36, which is adjustably mounted on the casing of the diathermy apparatus to permit ready movement of the electrode assembly 3| to the proper position relative to the subject, as may be desired. Also fixed to ring 33 are a trio of insulating brackets 31 whose outer ends hold an insulating ring 38 whose inner diameter approximates that of electrode assembly 3|.

In use, the insulating spacer ring 38 is placed touching the subject. Then electrode assembly 3| is adjusted to the proper spacing from the subject, and is fixed there by tightening screw 34. If desired, a stop can be used to prevent too small an air-spacing.

The construction of the electrode assembly 3| of Fig. 2 is shown in Fig. 3. The assembly '31 includes the electrode 4! formed by. a fiat spiral coil 42 with the outer turn it connected directly at M to the next innermost turn, so that turn 63 is a short-circuited turn or complete loop. The innermost end of coil 42 is connected to a terminal 48 having a square or other non-circular head and a threaded portion.

Electrode M is held between two disks d7, 68 of insulating sheet material. One disk, such as 47, may be recessed to accommodate electrode it, so that disk 48 acts as a cover plate. Disks 4! and 48 are fixed together, with electrode ii therebetween, in any suitable manner such as by insulating screws ts. Disk 41 is provided with an aperture Ell mating with the head of terminal 48 and through which terminal 46 has its threaded end engaged, the other end of the sleeve being connected tocable 29.

The elec.rode structure 3! constructed as just described. permits the use of airspacing technique while avoiding or minimizing substantially all the disadvantages of the prior art structure discussed above. By suitable design or the electrode structure (5 to 9 spiral turns for a 6-inch electrode), the voltage requirements for satisfactory treatment are materially reduced and the prior art sensitivity of adjustment is avoided. The complete theoretical. explanation of the operaion of this novel electrode is not fully understood, but is believed to be somewhat as follows: The coil 42 at the end of the cable 29 presents an effective distributed inductance which par.ially or wholl neutralizes the capacitance due to air-spacing and to the subject. This produces a greatly lowered impedance connected between the load ends of cables 29, 29a, so that for a given treatment eiiiect a much lower voltage is required across the load ends of the cables 28, 29a. This lowered load voltage refieced in a lowered terminal voltage, so that any likelihood of cable or condenser sparlz-over is greatly minimized. cuited outer turn prevents the existence of extreme potentials at the outer edge of the electrode coii which would otherwise occur. Such extreme potentials would tend to produce electrode-to-suppcrt spark-over and would increase the sensitivity of the apparatus to variation in subject position during treatment or to approach of externalbodies; by use oi the present invention these effects are greatly reduced. The shortcircuited turn also tends to render more uniform the field intensity variaLion with distance from the center; without the short-circuit, the field intensity rises rapidly toward the outer edge of the electrode, so that local circular heating of. the subject at the end of the electrode may be encountered. The short-circuited turn prevents the local peak field intensity, and makes the field intensity more nearly uniform from outer edge toward the center of the electrode. This outer closed turn also renders the tuning or adjustment less sensitive-that is, for a given condenser setting and high frequency current, a change in condenser adjuslment or movement of the subject produces less change in power delivered, through the use of the short-circuited turn.

The electrode coil 42 shown in Fig. 3 is formed of one continuous spiral of heavy copper or other In addition, the short-cir conductive wire, with'the outermost turn soldered or otherwise connected to the next inner turn. The wire may have any desired cross-section, such as round, elliptical, or square. No. 6 to No.

' 10 A. W. G. wire has been found highly satisfactory.

Operation of the invention may be further improved by making the outermost short-circuited turn relatively wide. This is shown in Fig. i, where the spiral wire coil "52 is connected to the inner edge of a wide flat ring 5! of conductive sheet or metal, forming the short-circuited turn. Ring 5! is preferably to 1 inch wide. The further peripheral capacitance provided by ring 56 appears to materially assist in the spark-over reduction and sensitivity inhibition provided by the present invention.

A further construction of electrode is shown in Fig. 5, where the electrode is formed out of a single circular sheet of conductive material, which has a spiral slot 53 formed concentrically therein. Such a slot leaves the remainder of the conductive material in the form of a spiral conductor of substantial width, while the short-circuited turn is formed by the integral outer portion 5 of the circular sheet. A slot about A; inch wide, with a spacing of A; to inch between successive slot turns and an outer ring of /2 to 1 inch in width have been found highly satisfactory, the exact radial width of conductor between slot turns being determined by the overall desired diameter of electrode and the desired number of coilturns. A convenient way of forming this electrode has been found to be by sawing or milling the slot. Another way is by electrodepositing conductive material upon a backing which is later stripped off, thedeposit being of the form shown in Fig. 5. Also stamping can be used.

Other forms of the present invention are schematically shown in Figs; 6 to 10. In Fig. 6, there is shown a spiral coil 56 whose innnermost end 59 is connected to a closed turn 58. If desired, turn 58 may be in the form of a solid disk. The outer end 57 of coil 56 is then connected to cable 29.

Fig. 7 shows another form in which the spiral coil 5% has its inner end 59 connected to a ring or disk 58 as in Fig. 6. However, in this case the outer end 5'! is connected to a shortcircuited turn iii, and cable 29 is connected to an intermediate point 62 of coil 58. Point 62 is preferably separated from outer turn 6| by /3 to /3 of the total number of turns. Outer turn 6! may be either a wire as in Fig. 3 or a wide ring as in Fig. 4..

In Figs. 8 to 10, a different type of electrode is shown, still embodying the basic principles of the present invention. In these figures, only a. single electrode is used on the subject treated, and both cables 29 and 29a are connected to it. It is highly useful for surface treatment of the subject, as distinguished from interior treatment. In Fig. 8, the coil 56 has its outer end 5'? connected to short-circuited turn 6! as in Figs. 3, 4 and 7. The inner end 59 is connected to cable 29a, while cable 29 is connected to coil 56 at an intermediate point 62, preferably to 1 6 the number of turns from end 59. In this way, coil 56 acts as an auto-transformer, and its high frequency magnetic field and electric field provide surface treatment.

In Fig. 9, the inner end 59 of coil 56 is connected to the inner short-circuited turn. or'disk 58, as in Figs. 6 and 7, while the outer end 51 is connected to cable 29. Cable 29a is then connected to an intermediate point 63, from to /3 the number of turns from end 51.

In Fig. 10, outer end 51 of coil 56 is connected to short-circuited turn 6!, while inner end 59 is connected to inner turn or disk 58, as in Fig. 7. Cables 29 and 29a are connected to intermediate points 64 and 65. Points 64 and 65 are separated about to the number of turns of coil 56, and are located intermediate the ends of coil 56, being preferably about equidistant between the innermost and outermost short-circuited turns.

It will be understood that Figs. 6 to 10 are schematic only, their construction being as described with respect to Figs. 3 to 5. Thus, in any of the modifications described, the short-circuited turn may be of the same wire as the coil itself, or may be a wide closed ring of sheet metal. The innermost turn when short-circuited may be a solid disk. Also, any of the forms described may be constructed out of an integral sheet by sawing or milling the necessary slot, as described relative to Fig. 5, or may be electrodeposited by electrochemical means so as to have any of the desired configurations described above.

Thus there has been described a novel and improved diathermy electrode incorporating distinctive features which overcome or minimize most of the disadvantages encountered in the use of current types of diathermy electrode. This apparently simple construction, however, has produced the long-sought improvement in diathermy apparatus.

While the above electrodes have been described as useful with diathermy apparatus, it will be understood that they are not so limited, but may also be used for analogous purposes, such as in high-frequency inductive heating apparatus.

Since many changes could be made without departing from the essential principles of the present inventions, it is to be understood that the above description and the appended drawings are illustrative only, and are not to be taken in a limiting sense, since the scope of the invention is defined by the appended claims.

I claim as my invention:

1. An electrode for a diathermy apparatus or the like comprising a flat spiral of electrically conductive material having one end connected to a coplanar short circuited turn and an electrical terminal on said spiral adapted to be connected to a lead-in conductor.

' 2. An electrode as in claim 1 wherein said shortcircuited turn surrounds said spiral.

3. An electrode as in claim 1 wherein said shortcircuited turn is surrounded by said spiral, the inner end of said spiral being connected to said turn.

4. An electrode as in claim 3 wherein a lead-in conductor is connected to the outer end of said spiral.

5. An electrode for diathermy apparatus or the like comprising a fiat spiral of conductive material having one end connected to a coplanar short-circuited turn, a lead-in conductor connected to the outer end of said spiral and a second lead-in-conductor connected to an intermediate point of said spiral.

6. An electrode for diathermy apparatus or the like comprising a flat spiral of conductive material having one end connected to a coplanar short-circuited turn, a lead-in conductor connected to said spiral, and a second short-circuited turn connected to the other end of said spiral, said lead-in conductor being connected to an intermediate point of said spiral.

7. An electrode as in claim 6, further including a second lead-in conductor connected to a different intermediate point of said spiral.

8. An electrode for diathermy apparatus or the like comprising a fiat spiral of conductive material having one end connected to a coplanar short-circuited turn, a lead-in conductor connected to said spiral, and a second lead-in conductor connected to said spiral and spaced from said first lead-in conductor.

9. An electrode as in claim 8 wherein said shortcircuited turn surrounds and is connected to the outer end of said spiral, one of said lead-in conductors being connected to the inner end of said spiral and the other to an intermediate point of said spiral.

10. An electrode for diathermy apparatus or the like comprising a flat spiral of conductive material having one end connected to a coplanar short-circuited turn, and a lead-in conductor connected to said spiral, said turn being surrounded by said spiral and connected to the inner end thereof, said lead-in conductor being connected to the outer end of said spiral, said electrode further including a second lead-in conductor connected to an intermediate point of said spiral.

11. An electrode for diathermy apparatus or the like comprising a coplanar conductive structure having a spiral section and a wide closed loop surrounding said spiral section and connected thereto, said electrode having a terminal for connection to a short wave generator.

12. An electrode for a diathermy apparatus or the like comprising a closed loop of conductive material having a radial dimension between A and '1 inch, a flat electrical inductance coil having one end connected to said loop and the other end of said coil having a terminal adapted to be connected to a lead-in conductor.

GERELD L. TAWNEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,130,758 Rose Sept. 20, 1938 FOREIGN PATENTS Number Country Date 203,396 Germany Oct. 20, 1908 280,387 Great Britain Nov. 17, 1927 

